Most vehicles include a fuel containment assembly which includes a tank which is selectively filled with gasoline or other types of vaporific fuels. The contained fuel is selectively communicated to and combusted within an engine, thereby allowing the vehicle to be driven. These fuel containment assemblies also typically include a vapor management system or assembly for transferring vapors, produced by the contained fuel, into a charcoal-filled canister and then into the vehicle's engine where the vapors are combusted. These vapors are typically toxic and their atmospheric emission from these fuel containment assemblies is undesirable. The containment tanks and vapor management systems are therefore required to be substantially "air-tight" or "sealed".
While these fuel containment assemblies substantially prevent the liquefied portion of the contained fuel from being undesirably discharged, they do not always substantially ensure that the vaporized portion of the fuel remains sealingly contained within the assembly. Sealingly containing the vaporized portion of the fuel is difficult due to the ability of the fuel vapors to rather easily traverse even small cracks or crevices within these assemblies. Moreover, as these fuel tanks and/or vapor management systems age, their respective joints and seams become porous, readily allowing the fuel vapors to undesirably leak into the environment. Accordingly, many governmental authorities have adopted relatively strict fuel vapor leakage guidelines and/or standards. Particularly, these authorities have mandated that automated leakage test systems be operatively provided within each vehicle, thereby allowing for the detection of such undesirable fuel vapor leaks and allowing the vehicle owner to quickly service and/or replace the leaking fuel containment assembly.
In order to correctly perform these various conventional and known fuel vapor leakage tests, it is necessary to have an accurate and current measurement of the amount of fuel vapor pressure existing within the vehicle's fuel containment tank and/or assembly. This pressure measurement is "made" or accomplished according to one of several known and conventional methods or techniques.
For example, vehicles having an "on-board" refueling vapor recovery system (typically referred to as an "ORVR type system") utilize a vapor pressure sensor which is selectively and operatively positioned within a fuel vapor line and which communicates with a "fill limiting vent valve". The fill limiting vent valve typically has a relatively large orifice (e.g., having a diameter of approximately 0.5 inches) which communicates with the fuel tank or fuel containment assembly. This large orifice allows the fuel vapor, emanating from the fuel tank, to be relatively easily communicated into the vapor line and into the operatively positioned vapor pressure sensor in a relatively unrestricted manner. Particularly, this relatively unrestricted flow of fuel vapor allows the pressure sensor to obtain substantially accurate and current measurements of the vapor pressure existing within the fuel tank and/or within the fuel containment assembly, thereby allowing for automated vapor leak detection.
While the previously delineated system adequately provides accurate fuel vapor pressure measurements, many vehicles do not have an "ORVR system" or a fill limiting vent valve and are not adapted to utilize the previously described "ORVR type" pressure sensor arrangement and/or vapor leakage methodology.
Particularly, many of these "non-ORVR" vehicles utilize a fuel tank mounted pressure sensor which is selectively and operatively "locked" into a stamped hole and which produces pressure measurements which are used to detect vapor leaks. The stamped hole is typically formed and/or located on the top surface of the fuel tank and is selectively "sealed" with a conventional and commercially available "o"-ring or other sealing device. This pressure sensing arrangement is undesirable due to the relatively high expense and/or cost of the tank mounted sensor and the relative difficulty and expense of installing and servicing the sensor.
To overcome some of the previously delineated drawbacks associated with "non-ORVR" pressure sensing arrangements, some attempts have been made to investigate the use of an "in-line" pressure sensor within "non-ORVR" type vehicles. These previous investigations and/or attempts have not been successful. Particularly, in these prior investigations and/or attempts, the pressure sensor was selectively and operatively positioned within a conventional fuel vapor line contained within the vapor system. Particularly, the fuel vapor line was connected between the charcoal canister and a conventional "roll-over" valve. The "roll over" valve was communicatively connected to the fuel tank and substantially prevented the leakage of liquid fuel from the tank into the vapor management system in the event of a "roll over" or other type of vehicle accident. Hence, the deployed pressure sensor communicated with the fuel tank by the cooperative use of the fuel vapor line and the "roll-over" valve.
This prior "in-line" and "non-ORVR" pressure sensor arrangement was unacceptable and substantially inoperable since the sensor was not able to reliably measure the fuel tank pressure due to the relatively small orifice (e.g., 0.04") of the "roll-over" valve.
Moreover, the relatively small diameter of the "roll over" valve orifice undesirably restricted the flow of vapor from the fuel tank to the deployed sensor and caused and/or created pressure surges or spikes within the sensor. These spikes and/or surges were incorrectly and undesirably interpreted as a vapor leak and produced "false alarms". Hence, based upon these prior experiences and/or investigations, it appeared as if a vapor leakage assembly having an "in line" pressure sensor could not be utilized in "non-ORVR" types of vehicles and/or systems, and that the concomitant benefits of these "in line" arrangements could not be realized in these "non-ORVR" vehicles or systems. Contrary to these prior experiences, Applicant has found that an "in-line" sensor may indeed be beneficially and operatively used in "non-ORVR" types of vehicle systems.
There is therefore a need for a new and improved vehicle fuel vapor leakage assembly having a pressure sensor which selectively and automatically measures the vapor pressure within a vehicle's fuel tank; which provides a relatively accurate, current, and selective measurement of the vapor pressure within the vehicle's fuel tank, effective to allow for the detection of fuel containment assembly vapor leakage; which is adapted for use within vehicles which do not contain or include an "ORVR system" or a fill limiting vent valve; which is relatively easy to install and maintain or service; and which provides these benefits in a relatively cost effective manner.